Formation compositional evaluation using normalized differential data

Abstract

A method for determining compositional data for fluids within a geological formation having a borehole therein may include collecting first and second dataset snapshots of the geological formation based upon measurements from the borehole at respective different first and second times, and with the borehole subject to fluid injection between the first and second times to displace fluids in the geological formation adjacent the borehole. The method may further include generating a differential dataset based upon the first and second dataset snapshots, normalizing the differential dataset to generate a normalized differential dataset, determining vertices defining a geometric shape and corresponding to respective different displaced fluid signatures based upon the normalized differential dataset, and determining displaced compositional data with respect to the different displaced fluid signatures based upon a position of a datapoint from the normalized differential dataset on the geometric shape.

That which is claimed is: 
     
         1 . A method for determining compositional data for fluids within a geological formation having a borehole therein, the method comprising:
 collecting first and second dataset snapshots based upon measurements of the geological formation from the borehole at respective different first and second times, and with the borehole subject to fluid injection between the first and second times to displace fluids in the geological formation adjacent the borehole;   generating a differential dataset based upon the first and second dataset snapshots;   normalizing the differential dataset to generate a normalized differential dataset;   determining vertices defining a geometric shape and corresponding to respective different displaced fluid signatures based upon the normalized differential dataset; and   determining displaced fluid compositional data with respect to the different displaced fluid signatures based upon a position of a datapoint from the normalized differential dataset on the geometric shape.   
     
     
         2 . The method of  claim 1  wherein the measurements comprise different respective log measurement types; and wherein determining the vertices further comprises determining the normalized differential dataset as a cross-plot with a respective dimension for each log measurement type. 
     
     
         3 . The method of  claim 1  wherein collecting the first and second dataset snapshots comprises collecting the first and second datasets using a logging-while-drilling (LWD) tool during a drill pass and a wipe pass, respectively. 
     
     
         4 . The method of  claim 1  wherein the first and second dataset snapshots comprise at least one of gamma ray measurement data, neutron measurement data, density measurement data, and thermal neutron capture cross-section data. 
     
     
         5 . The method of  claim 1  wherein normalizing comprises normalizing data points from the differential dataset to coincide with the surface of a sphere. 
     
     
         6 . The method of  claim 1  wherein normalizing comprises normalizing data points from the differential dataset to coincide with the surface of a two-dimensional plane. 
     
     
         7 . The method of  claim 1  wherein the geometric shape comprises a geodesic triangle. 
     
     
         8 . The method of  claim 1  wherein the displaced fluid signatures correspond to displaced injection water, displaced connate water, and at least one displaced hydrocarbon fluid. 
     
     
         9 . A well-logging system comprising:
 a well-logging tool to collect first and second dataset snapshots based upon measurements of a geological formation from a borehole within the geological formation at respective different first and second times, and with the borehole subject to fluid injection between the first and second times to displace fluids in the geological formation adjacent the borehole; and   a processor to
 generate a differential dataset based upon the first and second dataset snapshots, 
 normalize the differential dataset to generate a normalized differential dataset, 
 determine vertices defining a geometric shape and corresponding to respective different displaced fluid signatures based upon the normalized differential dataset, and 
 determine displaced fluid compositional data with respect to the different displaced fluid signatures based upon a position of a datapoint from the normalized differential dataset on the geometric shape. 
   
     
     
         10 . The well-logging system of  claim 9  wherein the measurements comprise different respective log measurement types; and wherein said processor determines the vertices further as a cross-plot with a respective dimension for each measurement type. 
     
     
         11 . The well-logging system of  claim 9  wherein said well-logging tool comprises a logging-while-drilling (LWD) tool to collect the first and second dataset snapshots during a drill pass and a wipe pass, respectively. 
     
     
         12 . The well-logging system of  claim 9  wherein the first and second dataset snapshots comprise at least one of gamma ray measurement data, neutron measurement data, density measurement data, and thermal neutron capture cross-section data. 
     
     
         13 . The well-logging system of  claim 9  wherein said processor normalizes data points from the differential dataset to coincide with the surface of a sphere. 
     
     
         14 . The well-logging system of  claim 9  wherein said processor normalizes data points from the differential dataset to coincide with the surface of a two-dimensional plane. 
     
     
         15 . The well-logging system of  claim 9  wherein the displaced fluid signatures correspond to displaced injection water, displaced connate water, and at least one displaced hydrocarbon fluid. 
     
     
         16 . A non-transitory computer-readable medium having computer executable instructions for causing a computer to:
 generate a differential dataset from first and second dataset snapshots based upon measurements of a geological formation collected from a borehole within the geological formation at respective different first and second times, and with the borehole subject to fluid injection between the first and second times to displace fluids in the geological formation adjacent the borehole;   normalize the differential dataset to generate a normalized differential dataset;   determine vertices defining a geometric shape and corresponding to respective different displaced fluid signatures based upon the normalized differential dataset; and   determine displaced fluid compositional data with respect to the different displaced fluid signatures based upon a position of a datapoint from the normalized differential dataset on the geometric shape.   
     
     
         17 . The non-transitory computer-readable medium of  claim 16  wherein the first and second datasets comprise at least one of gamma ray measurement data, neutron measurement data, density measurement data, and thermal neutron capture cross-section data. 
     
     
         18 . The non-transitory computer-readable medium of  claim 16  wherein data points from the differential dataset are normalized to coincide with the surface of a sphere. 
     
     
         19 . The non-transitory computer-readable medium of  claim 16  wherein data points from the differential dataset are normalized to coincide with the surface of a two-dimensional plane. 
     
     
         20 . The non-transitory computer-readable medium of  claim 16  wherein the displaced fluid signatures correspond to displaced injection water, displaced connate water, and at least one displaced hydrocarbon fluid.